The effect of hydrogen bonding on the copolymerization kinetics of 2‐methoxyethyl acrylate with 2‐hydroxyethyl methacrylate in alcohol and aqueous solutions

Abstract

AbstractThe influence of alcohol and alcohol/water solutions on the radical copolymerization kinetics of 2‐hydroxyethyl methacrylate (HEMA) with 2‐methoxyethyl acrylate (MEA) is studied using pulsed‐laser‐polymerization coupled with size exclusion chromatography. It is found that MEA incorporation into the copolymer is increased in butanol, methanol (MeOH), and MeOH/H2O solutions relative to the bulk system. Copolymer composition can be represented for solvent levels ≥50 vol.% by a single pair of reactivity ratios ( = 2.39 ± 0.16, = 0.28 ± 0.02) that differ from those in bulk ( = 3.14 ± 0.44, = 0.27 ± 0.04). MeOH as solvent slightly reduces the propagation rate coefficient of HEMA compared to the bulk system, in contrast to the increase in the MEA value. Thus, the value of is higher in MeOH for MEA‐rich systems compared to bulk, with the effect of the solvent reduced as the HEMA content in the comonomer mixture is increased. Adding water as cosolvent significantly increases values for both monomers, with in MeOH/H2O higher than bulk values over the complete composition range. Furthermore, for 50% monomer in the solvent systems studied can be represented by the implicit penultimate unit model using a single pair of radical reactivity ratios. It is concluded that the strongest influence of hydrogen‐bonding solvents compared to bulk is on the homopropagation values, rather than on copolymerization parameters, and that the difference in relative reactivity of non‐functional and functional monomers in bulk and aqueous solution should be accounted for when studying emulsion copolymerization.